We have developed a number of powerful techniques for studying singlet oxygen and some other strong xidants. These techniques include laser flash spectroscopy, direct detection of singlet oxygen in solution by infrared phosphorescence, kinetic techniques for characterizing reactive species and determining reaction mechanisms, and specific trapping agents which may be used even with living systems. This proposal suggests methods of extending the techniques we have developed to further systems which provide models for targets of oxygen damage, and of developing new, more powerful methods for establishing mechanisms at the molecular level and of trapping reactive species. Studies of the reactions of singlet oxygen with biologically important target molecules using these techniques are proposed, along with methods for detecting and quantitating its appearance in biological systems. These studies will be extended to include other reactive oxygen species (such as superoxide ion and hydroxyl radical) that are of interest to a wide range of fields in the areas of biology and medicine. These techniques will also allow us to study the mechanism by which certain reactions related to enzymatic processes cause the oxidation of organic compounds. The interrelationship between singlet oxygen, superoxide ion, and hydroxyl radical will be studied. We will extend new findings about the relationship between hypochlorous acid production and the mechanism of antimicrobial action leucocytes, land design specific systems to trap possible oxidizing species in specific locations in these cells.